Zone theory is that we are fat because our insulin levels are thrown all over the place by our modern diet, especially the USDA food pyramid kind of diet with pasta and bread at the bottom. If you control insulin levels, you control your general health. Maintain insulin levels in 'the Zone' and you become healthy. If you become healthy and are overweight, you automatically lose weight. A 'Zone Meal' just looks incredibly healthy, an Atkins meal does not.
I'm not trying to knock these 'unconventional' diets - I don't know enough to - but aren't they at odds with what I've always believed to be an well-documented increase in health problems in places that have switch from their traditional low fat/high carbohydrate diets to a 'western' higher-fat diet (e.g. the mediterranean and I believe Japan) over the past half-century?